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Author Topic: Image from prime vs. downsized image from zoom  (Read 2583 times)
AreBee
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« on: December 14, 2013, 11:30:58 AM »
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Folks,

Say that a prime lens is wide enough to capture a composition but too wide to frame it exactly. Assume a zoom can frame the composition exactly.

Most, though not all primes perform better than zooms at the same focal length. Assume that is the case here.

For the same persepective an image from the zoom will have greater resolution than the prime because the composition is assumed to have been framed exactly with the former and cropped from the image obtained from the latter. Therefore, we can afford to downsize the image from the zoom and in so doing improve its quality.

Question: Is it possible for a downsized image from a zoom to be technically superior to the cropped image from a prime, even though optically the prime is superior to the zoom at the same focal length? I appreciate that the answer may depend on which prime and zoom is considered. I do not have any particular lenses in mind. What I am looking for is to get a feel for how likely a zoom could best a prime. For example, the answer may be that it is possible but the prime would require to be of atrocious quality for that to occur.

Cheers,
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ErikKaffehr
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« Reply #1 on: December 14, 2013, 11:57:35 AM »
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Hi,

It's hard to say, if you use medium apertures any good lens will be quite close to diffraction limits. Good zooms can give primes a run for they money.

If a prime is significantly better than a zoom, the zoom may still win if the crop factor is significant enough.

I don't have that much experience, I have good zooms and I don't have a lot of good primes.

Best regards
Erik

Folks,

Say that a prime lens is wide enough to capture a composition but too wide to frame it exactly. Assume a zoom can frame the composition exactly.

Most, though not all primes perform better than zooms at the same focal length. Assume that is the case here.

For the same persepective an image from the zoom will have greater resolution than the prime because the composition is assumed to have been framed exactly with the former and cropped from the image obtained from the latter. Therefore, we can afford to downsize the image from the zoom and in so doing improve its quality.

Question: Is it possible for a downsized image from a zoom to be technically superior to the cropped image from a prime, even though optically the prime is superior to the zoom at the same focal length? I appreciate that the answer may depend on which prime and zoom is considered. I do not have any particular lenses in mind. What I am looking for is to get a feel for how likely a zoom could best a prime. For example, the answer may be that it is possible but the prime would require to be of atrocious quality for that to occur.

Cheers,
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Telecaster
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« Reply #2 on: December 14, 2013, 03:11:15 PM »
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Say that a prime lens is wide enough to capture a composition but too wide to frame it exactly. Assume a zoom can frame the composition exactly.

Get in closer with the prime, et Voilà! Not always possible, of course, but in many situations it should be.

I guess I don't get the purpose of trying to establish a better/worse scenario here. Lenses are just tools. Use the one(s) most appropriate for the situation. If you're caught out lacking the best choices, make do with what you've got.

I once spent 10 days at the Grand Canyon with a nearly new camera and just one lens, a 90mm macro, 'cuz my 28–70mm didn't arrive in time for the trip (my fault for trying to buy late...local dealer was out of stock) and the 70–200mm's focusing mechanism jammed on the first day. Bad planning on my part. But I made do and actually had a great time snapping away. I also made a number of multi-shot compositions with the intent of eventually stitching 'em together. (This was in 1993...film, early days of affordable scanners, modest computing power, fairly crude editing software.) Which in due course I did.

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Question: Is it possible for a downsized image from a zoom to be technically superior to the cropped image from a prime, even though optically the prime is superior to the zoom at the same focal length?

Again, is there a practical purpose behind this...like downsizing for screen display or a small-ish print?

Let's explore a hypothetical: one photo taken with an 80–400mm at the long end; and a second photo taken with a 105mm & cropped to the same field-of-view as the first photo. We're using the latest Wunderkind Kamera, the Sony A7r, at optimal settings so as to avoid the dreaded shutter shock phenomenon.   Wink  Both photos printed at 240ppi with the cropped prime pic at full size and the zoom pic downsampled to match. I'd likely accept the cropped prime pic...it should look good. But I suspect the zoom pic will make for a nicer print, even assuming a meh-performing lens. More sub-samples per pixel. This assumes skilled post work with each photo.

Now in the real world I'd never do this. I mean in terms of making a direct comparison. I've printed plenty of extreme crops from both primes and zooms, but they've been a better make do kinda thing as with my Grand Canyon example above. Given the option of using a more appropriate tool, that's what I'll use.

-Dave-
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Petrus
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« Reply #3 on: December 14, 2013, 03:32:50 PM »
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Practical example ("practical"?) using DxO lens data:

Best lens in the database for Nikon bodies is the Zeiss Otus 55 mm with 29 MPix resolution on Nikon D800. Best zoom in the same range is the Tamron 24-70mm with 17 MPix resolution. With crude second grade math we can deduce that we could enlarge the Otus picture by (29/17)/sqr2 = 1.2 linear which means that shooting the Tamron at 66mm zoom setting would give the same resolution as the Otus frame cropped to the same size. This would give the Otus the digital zoom range of 55-66mm. Not much.

Get a zoom.
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ErikKaffehr
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« Reply #4 on: December 14, 2013, 03:50:57 PM »
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Hi,

I would suggest that most good zooms are within 20% or so of the best primes. I would say that an 70-200 zoom at 120 mm always wins over an 85 mm prime, unless the zoom is junk.

20% is a lot. It corresponds to the difference between 24 MP and 36MP.

I don't use primes, because I cannot see a difference the way I shoot. The enclosed image shows a comparison of my 24-70/2.8 with  the Zeiss Otus at 55 mm and f/8, yes the Otus is better, but I guess the difference is to small to be detected in an A2 print.

If you are shooting at f/1.4, the Otus is probaby without competition, but at f/8, I don't think I care.

Best regards
Erik



Get in closer with the prime, et Voilà! Not always possible, of course, but in many situations it should be.

I guess I don't get the purpose of trying to establish a better/worse scenario here. Lenses are just tools. Use the one(s) most appropriate for the situation. If you're caught out lacking the best choices, make do with what you've got.

I once spent 10 days at the Grand Canyon with a nearly new camera and just one lens, a 90mm macro, 'cuz my 28–70mm didn't arrive in time for the trip (my fault for trying to buy late...local dealer was out of stock) and the 70–200mm's focusing mechanism jammed on the first day. Bad planning on my part. But I made do and actually had a great time snapping away. I also made a number of multi-shot compositions with the intent of eventually stitching 'em together. (This was in 1993...film, early days of affordable scanners, modest computing power, fairly crude editing software.) Which in due course I did.

Again, is there a practical purpose behind this...like downsizing for screen display or a small-ish print?

Let's explore a hypothetical: one photo taken with an 80–400mm at the long end; and a second photo taken with a 105mm & cropped to the same field-of-view as the first photo. We're using the latest Wunderkind Kamera, the Sony A7r, at optimal settings so as to avoid the dreaded shutter shock phenomenon.   Wink  Both photos printed at 240ppi with the cropped prime pic at full size and the zoom pic downsampled to match. I'd likely accept the cropped prime pic...it should look good. But I suspect the zoom pic will make for a nicer print, even assuming a meh-performing lens. More sub-samples per pixel. This assumes skilled post work with each photo.

Now in the real world I'd never do this. I mean in terms of making a direct comparison. I've printed plenty of extreme crops from both primes and zooms, but they've been a better make do kinda thing as with my Grand Canyon example above. Given the option of using a more appropriate tool, that's what I'll use.

-Dave-
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k bennett
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« Reply #5 on: December 14, 2013, 03:56:59 PM »
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Get in closer with the prime, et Voilà! Not always possible, of course, but in many situations it should be.

But this changes the camera postion and, by definition, the perspective of the photo (the relationship between the background and foreground objects.) In my mind, camera position is one of the, if not the, most important decision the photographer can make, and the whole notion of "zooming with your feet" is less than optimal.
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ErikKaffehr
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« Reply #6 on: December 14, 2013, 04:03:41 PM »
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Hi,

You cannot zoom with your feet, as you state, moving changes your composition/perspective. It is very well possible that a set of boundary conditions forces you into a better perspective, tough.

Ground is not always flat. Climbing up or down changes perspective. I often move my camera just a few inches to get a better composition, but it is well possible that you walk up a small hill and get a better composition.

Best regard
Erik

But this changes the camera postion and, by definition, the perspective of the photo (the relationship between the background and foreground objects.) In my mind, camera position is one of the, if not the, most important decision the photographer can make, and the whole notion of "zooming with your feet" is less than optimal.
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AreBee
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« Reply #7 on: December 14, 2013, 05:46:19 PM »
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Dave,

Quote from: Telecaster
Get in closer with the prime, et Voilà! Not always possible, of course, but in many situations it should be.

I agree fully with K Bennet (refer above for post): when the location that returns the strongest composition has been determined, any change in location will reduce its strength. This will be exacerbated for compositions of wide FOV whereby a small change in location can change the compositon dramatically.

Moving position is not an option. It is for this reason that I wrote "For the same persepective ..." in my original post.

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I guess I don't get the purpose of trying to establish a better/worse scenario here.

Allow me to explain. I shoot predominantly with zooms because I prefer to frame tight and benefit fully from the resolution on offer by the camera. I also shoot predominantly at f/8 and am aware that the difference between primes and zooms converges at smaller apertures.

My question was intended to inform possible lens purchase(s) - if the consensus of responses was that there is little or no difference between a cropped prime and downsized zoom then there is no reason for me to purchase primes (unless a composition is only marginally less in FOV, or exactly matches the FOV of a particular prime, and I wish to obtain the absolute last bit of performance from a lens, in which case according to my cost/value relationship it may be worthwhile obtaining a prime).

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Lenses are just tools. Use the one(s) most appropriate for the situation.

I agree. However, my question was aimed at the possible acquisition of lenses rather than selecting from those I currently own. I appreciate that you were not aware of this.

Petrus,

Quote from: Petrus
...shooting the Tamron at 66mm zoom setting would give the same resolution as the Otus frame cropped to the same size. This would give the Otus the digital zoom range of 55-66mm. Not much.

Get a zoom.

 Smiley Thanks. I agree that 55-66mm is not much, but what about at wide or extreme wide FOV, where a small difference in focal length returns a disproportionate difference in FOV (in comparison to a focal length of the order of the 55mm)?

Erik,

Quote from: ErikKaffehr
I would say that an 70-200 zoom at 120 mm always wins over an 85 mm prime, unless the zoom is junk.

You mean an image at 120mm downsized to that of an image at 85mm? Why do you consider that the former "always wins"?

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The enclosed image shows a comparison of my 24-70/2.8 with  the Zeiss Otus at 55 mm and f/8...

Thanks for this information, but shouldn't the 24-70mm results be at f/8 in order to be comparable on a like for like basis with the Otus?

Cheers,
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Telecaster
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« Reply #8 on: December 14, 2013, 09:12:20 PM »
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But this changes the camera postion and, by definition, the perspective of the photo (the relationship between the background and foreground objects.) In my mind, camera position is one of the, if not the, most important decision the photographer can make, and the whole notion of "zooming with your feet" is less than optimal.

This assumes your original position, and thus perspective, is optimal. Unless you move to "better" frame your composition with whatever focal length you're using, how will you know? If it turns out you have to move back (or even further forward) to get the right spatial relationships, then you do so and 1) crop your shot in post, 2) switch to a different lens or 3) adjust your zoom. But IMO it's always best to explore, even if you see something interesting in the viewfinder and press the shutter button right then & there. The initial impulse is often the best one, but not always.

-Dave-
« Last Edit: December 14, 2013, 09:16:21 PM by Telecaster » Logged
AreBee
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« Reply #9 on: December 15, 2013, 04:40:17 AM »
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Folks,

I figured out from Erik's DxO plot how to generate one myself. I have pitted my 24-70mm Nikkor (at 50mm) against the Zeiss 55mm Otus. Smiley Both are at f/8.

I can't honestly say I understand what it is I am seeing other than that the results are close (close? very close? near-identical?). However, this raises an additional question:

In the Medium Format forum I have read several times that a technical camera with MFDB and the best RS or SK lenses "destroys" 35mm format results, and that it is "not close". Is this true for landscape photography, where shooting at small apertures is the norm? After all, there appears to be very little difference between the finest ~50mm prime vs a zoom.
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ErikKaffehr
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« Reply #10 on: December 15, 2013, 06:05:09 AM »
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Hi,

1) Comparing an uncropped 120 shot vs. a cropped 85 mm shot.

2) The Otus performs best at f/5.6 while the 24-70/2.8 zoom still improves at f/8, maybe. I would presume that I would shoot each at optimum aperture.

Best regards
Erik

Dave,

Erik,

You mean an image at 120mm downsized to that of an image at 85mm? Why do you consider that the former "always wins"?

Thanks for this information, but shouldn't the 24-70mm results be at f/8 in order to be comparable on a like for like basis with the Otus?

Cheers,
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ErikKaffehr
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« Reply #11 on: December 15, 2013, 06:21:15 AM »
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Hi,

That is a small difference. Something like stopping down from f/5.6 to f/11 on the same lens. The great performance win of the Otus is at large apertures.
There is more to image quality than sharpness. Out of focus rendering is important, too.

I happen to shoot both MF and 135. P45+ (39 MP) with Zeiss lenses and Sony Alpha 99 (24 MP). Very clearly, achievable sharpness on the P45+ is better than on Alpha 99.

A couple of months ago I shot the same subject with the P45+ using my Sonnar 150/4 and Alpha 99 with my 70-400/4-5.6. Using the zoom I cropped tighter, and that essentially eliminated the MG advantage of the P45+. I made identical crops corresponding to 22x34" (57x86 cm) and printed on A4 paper. I cannot tell the prints apart except some detail near the edge where the P45+ wins.

Actual pixels crops from that image. Second crop was indistinguishable while the first crop was visible better on the P45+.

Best regards
Erik

Folks,

I figured out from Erik's DxO plot how to generate one myself. I have pitted my 24-70mm Nikkor (at 50mm) against the Zeiss 55mm Otus. Smiley Both are at f/8.

I can't honestly say I understand what it is I am seeing other than that the results are close (close? very close? near-identical?). However, this raises an additional question:

In the Medium Format forum I have read several times that a technical camera with MFDB and the best RS or SK lenses "destroys" 35mm format results, and that it is "not close". Is this true for landscape photography, where shooting at small apertures is the norm? After all, there appears to be very little difference between the finest ~50mm prime vs a zoom.
« Last Edit: December 15, 2013, 06:38:36 AM by ErikKaffehr » Logged

AreBee
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« Reply #12 on: December 15, 2013, 07:26:21 AM »
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Erik,

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That is a small difference. Something like stopping down from f/5.6 to f/11 on the same lens.

Hmm. That is a not insignificant difference to me, albeit I accept the difference is small.

Quote
There is more to image quality than sharpness.

Yes, I appreciate that. Smiley

Quote
Actual pixels crops from that image. Second crop was indistinguishable while the first crop was visible better on the P45+.

Agreed on both counts, assuming the visibly better P45+ corresponds to the left of the first pair of crops. Do you have an explanation for the difference in the first pair of crops? Are they corner crops? Was there any wind during capture?
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PhotoEcosse
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« Reply #13 on: December 15, 2013, 11:50:49 AM »
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Get in closer with the prime, et Voilà!

-Dave-


as long as the change in perspective is acceptable.
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k bennett
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« Reply #14 on: December 15, 2013, 01:46:10 PM »
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This assumes your original position, and thus perspective, is optimal. Unless you move to "better" frame your composition with whatever focal length you're using, how will you know?

Well, yeah, ok. Duh. Nobody is suggestion that one is limited to a single attempt at finding the right camera position. But once the perfect spot is located, then AreBee's original question remains, and the suggestion to just "walk in closer with the prime" is still rather lmited.

That's one reason I have preferred zoom lenses when using a tripod, especially for landscapes and architecture. I can find the proper camera position, then frame the final image exactly the way I want. The only current exception to this is my Fuji 14mm prime, which is just a wonderful wide angle and I end up using it a lot, both on a tripod and for candid, more fluid shooting opportunites.
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ErikKaffehr
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« Reply #15 on: December 15, 2013, 01:53:48 PM »
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Hi,

The crops are edge crops on 135. The Sonnar 150 was a bit wider, so it is a bit from the edge. I could not go closer with the Sonnar, as I am standing on a road bank, giving me some height. Moving one meter forward changes POV badly. Moving back means standing on the road and it is a busy one. I could stand on the other side but then I would have power wires hanging into my image (I have tried that, too!).

It could also be focusing related. With live view on the A99 at 11X magnification I have perfect focus. THe Hasselblad I cannot focus that exactly and I think I may have a small tendency to front focus.

Regarding wind, it is always windy in Sweden, just a question on how windy?

Best regards
Erik

Erik,

Hmm. That is a not insignificant difference to me, albeit I accept the difference is small.

Yes, I appreciate that. Smiley

Agreed on both counts, assuming the visibly better P45+ corresponds to the left of the first pair of crops. Do you have an explanation for the difference in the first pair of crops? Are they corner crops? Was there any wind during capture?
« Last Edit: December 15, 2013, 02:25:30 PM by ErikKaffehr » Logged

Telecaster
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« Reply #16 on: December 15, 2013, 03:35:32 PM »
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Well, yeah, ok. Duh. Nobody is suggestion that one is limited to a single attempt at finding the right camera position. But once the perfect spot is located, then AreBee's original question remains, and the suggestion to just "walk in closer with the prime" is still rather lmited.

Just to clarify, the et Voilà! in my earlier post was intended to indicate a certain jesting aspect to my response. This was apparently swamped by the more serious tone elsewhere in the post. Oy...

In reality when approaching a subject/composition there is no single right perspective or position. When I'm using a single-focal-length lens I view the world via its constraints. I often find this useful in filtering out options and concentrating my ability to see. When I'm using a zoom I take a more free-wheeling approach. Both are good. The "zoom vs. prime" argument is to me meaningless.

Re. the original post...to the extent that it has any real-world orientation, it's in this: given a sensor with a high enough photosite density, an average lens framed optimally will likely deliver a technically superior result to a great lens framed sub-optimally such that the resulting great lens photo requires significant (or in some cases merely modest) cropping. This assumes optimal technique, of course. (Note that I'm just rephrasing and slightly augmenting the conclusion I came to in my first post.) Prime or zoom...doesn't matter.

-Dave-
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ErikKaffehr
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« Reply #17 on: December 15, 2013, 04:45:26 PM »
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Hi,

I have been shooting zooms lately, but in the summer I bought a Hasselblad with a digital back and five lenses. So now I use both in parallell. The Hasselblad lacks the focal length range of the DSLR, I use lenses from 12mm up to 800mm. So when I go for a short walk I carry both, that is seven lenses plus a tripod ;-(

Now, what I have seen is that I am more constrained with the "Blad", but the compositions are often more compelling. I cannot take the picture I want, I need a compromise and that sometimes turns out better than the original idea. With the "Blad" I often expand field of view by stitching. On the DSLR I would zoom out a bit, but with the Hasselblad my choice may be to go from say 80 mm to say 50 mm (instead of 75). So I stitch. That works well.

Best regards
Erik




Just to clarify, the et Voilà! in my earlier post was intended to indicate a certain jesting aspect to my response. This was apparently swamped by the more serious tone elsewhere in the post. Oy...

In reality when approaching a subject/composition there is no single right perspective or position. When I'm using a single-focal-length lens I view the world via its constraints. I often find this useful in filtering out options and concentrating my ability to see. When I'm using a zoom I take a more free-wheeling approach. Both are good. The "zoom vs. prime" argument is to me meaningless.

Re. the original post...to the extent that it has any real-world orientation, it's in this: given a sensor with a high enough photosite density, an average lens framed optimally will likely deliver a technically superior result to a great lens framed sub-optimally such that the resulting great lens photo requires significant (or in some cases merely modest) cropping. This assumes optimal technique, of course. (Note that I'm just rephrasing and slightly augmenting the conclusion I came to in my first post.) Prime or zoom...doesn't matter.

-Dave-
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Telecaster
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« Reply #18 on: December 16, 2013, 03:03:57 PM »
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Now, what I have seen is that I am more constrained with the "Blad", but the compositions are often more compelling. I cannot take the picture I want, I need a compromise and that sometimes turns out better than the original idea. With the "Blad" I often expand field of view by stitching. On the DSLR I would zoom out a bit, but with the Hasselblad my choice may be to go from say 80 mm to say 50 mm (instead of 75). So I stitch. That works well.

I've long been a fan of stitching, as mentioned above re. the Grand Canyon. Out of necessity earlier on but more recently by choice. When I lived in the Middle East in the mid-1980s I made a number of multi-shot compositions, then later physically cut & pasted prints together to form the final images. Probably got the idea from David Hockney's "joiners," though I wasn't interested in collages per se. I've always liked broad compositions but have never much cared for the way ultra-wide lenses draw in the viewfinder. (Even though I've owned & used some.) Electronic photography has been a big plus in this regard. With the Pentax 645D I'd mostly rather take two or three shots with a 55mm lens & then bang 'em together into a pano than take a single 35mm pic. Other people do great work with wide lenses, though...

-Dave-
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« Reply #19 on: December 16, 2013, 03:16:12 PM »
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If the subject matter, composition, lighting, and similar factors are good, then either way will result in a good photo. If they are not, then both ways will result in crap. My respectful suggestion is to pay more attention to the photo and less to the equipment.
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