Tele-converter or DX mode

[NorthernFocus]

charts and the little calculator are handy and all, but they don't illustrate anything in the real world. we can spend all day talking about how stuff works in theory, but I'm interested in what actually happens in practice. I'm asking if you (or anyone) has pictures that illustrate it

@Steve has done some good work on this topic and demonstrates it in his videos. I'd post a link but you can search them as well as I can.

because from what I can tell, whether DOF does or does not change - the impact on the final image isn't significant

If it's not significant to you then there's your answer. It's about perception and if you don't perceive the difference then there's no effect. Simple. Discussion beyond that is everyone elses opinion. Or math which doesn't seem to carry much weight.

evidently decades of people debating it - and the reason people can't come to a conclusion is because it's not an impact that is easy to point out.

And perhaps much discussion that's heavily weighted by confirmation bias.

a person will never know based on DOF, whether an image is fullsize or cropped - unless compared to a fullsize or cropped image of itself - which never happens outside of testing.

Sure it happens outside of testing. It happens right there on your own monitor every time you crop an image. If you don't see it I'd call it a happy day. No need to spend big bucks on wide aperture long prime lenses

 

[fcotterill]

These two articles review these interrelated subjects

Sensor Crop Factors and Equivalence

photographylife.com

Sensor Size, Perspective and Depth of Field

photographylife.com

 

[nmerc_photos]

@Steve has done some good work on this topic and demonstrates it in his videos. I'd post a link but you can search them as well as I can.

If it's not significant to you then there's your answer. It's about perception and if you don't perceive the difference then there's no effect. Simple. Discussion beyond that is everyone elses opinion. Or math which doesn't seem to carry much weight.

And perhaps much discussion that's heavily weighted by confirmation bias.

Sure it happens outside of testing. It happens right there on your own monitor every time you crop an image. If you don't see it I'd call it a happy day. No need to spend big bucks on wide aperture long prime lenses

put it this way - is whatever DOF happens or change is perceived, significant enough that it warrants being a pro or a con in the discussion of TC vs crop?

that's what I (and I think OP) are ultimately asking. If I was to make a pro con list of both - with my current knowledge, DOF wouldn't make the list.

less pixels on subject, significantly noticeable
more noise in image, significantly noticeable
reduced aperture, significantly noticeable
reduced IQ from TC, significantly noticeable
DOF? - noticeable? not noticeable? does anyone claim it is significantly noticeable?

or are we just throwing it out there for funsies? "hey it is something that changes - even though you'd never know anything changed unless I showed you a before and after"?

are there people out there who consider the affect cropping will have on their DOF when making an image? would someone ever throw away an image because they thought "my subject is too far, if I have to crop in my DOF is going to be ruined!"? or conversely, are there people who specifically choose to crop because they perceive value in shallower DOF?

not trying to be snarky or dismiss anything you're saying - I'm trying to understand what's going on. after spending hours googling and youtubing "does cropping affect DOF, cropping and DOF example, is cropping DOF significant", etc. I'm not coming up with anything that illustrates a difference or anyone who is even saying that it does have a significant difference.

even you haven't said it's significant. just that it's something that exists and is measurable numerically.

 

[bleirer]

As they try to demonstrate in the advanced calculator I linked earlier, the circle of confusion is linked to the visual acuity of the observer, the size of the image, and the viewing distance. I agree that if I took an 8x10 print and held it at arms length then cut a 4x5 print out of the center and held that at arms length there would be no difference in DOF. After all it is the exact same print. But once I view that 4x5 more closely, or blow the cropped 4x5 back up to 8x10 and held it at arms length there would be a reduction in dof that would track with the crop factor.

The reason the calculator shows a difference is they make the assumption that the cropped portion is going to be enlarged to be viewed at the same size and distance. If they didn't make that assumption the math would yield no difference because the c of c only changes when the viewing size or distance changes.

 

[John Navitsky]

The reason the calculator shows a difference is they make the assumption that the cropped portion is going to be enlarged to be viewed at the same size and distance. If they didn't make that assumption the math would yield no difference because the c of c only changes when the viewing size or distance changes.

this!

and that assumption turns it from easy to understand concept into a brain twister

 

[John Navitsky]

and again.. practicality..

does anyone think when i decided to put on the tc instead of crop it was because i was thinking hard about the effective dof or image noise or whatever?

and more importantly, do you think i really should have been?

and do you think you’ll look at the resulting images and shake your head because i was a bonehead and ruined my images for running in crop or with the tc?

and do you think you should generalize those conclusions to say you should or should not crop or run with a tc?

ie, do you really think there is A answer to that question

 

[bleirer]

and again.. practicality..

does anyone think when i decided to put on the tc instead of crop it was because i was thinking hard about the effective dof or image noise or whatever?

and more importantly, do you think i really should have been?

and do you think you’ll look at the resulting images and shake your head because i was a bonehead and ruined my images for running in crop or with the tc?

and do you think you should generalize those conclusions to say you should or should not crop or run with a tc?

ie, do you really think there is A answer to that question

I usually crop because I ran out if reach on my lens, or I am unsure of composition and want to leave a little wiggle room.

 

[John Navitsky]

I usually crop because I ran out if reach on my lens, or I am unsure of composition and want to leave a little wiggle room.

right, we act practically based on our specific situation and gear

 

[Doug Herr]

Reading through this thread it has become apparent that we'd be more likely to reach consensus if we were discussing protection filters.

Me? I like IQ & PPD (Pixels Per Duck) and I use the equipment that gets me the IQ I want with the PPD I want. Atmospheric distortion usually ends up making the hair-splitting over To TC or Not To TC a moot point. YMMV.

 

[NorthernFocus]

put it this way - is whatever DOF happens or change is perceived, significant enough that it warrants being a pro or a con in the discussion of TC vs crop?

that's what I (and I think OP) are ultimately asking. If I was to make a pro con list of both - with my current knowledge, DOF wouldn't make the list.

In that context you're spot on. A 1.4x TC or an equivalent 1.4x crop in post has the same net effect on DOF.

 

[bleirer]

In that context you're spot on. A 1.4x TC or an equivalent 1.4x crop in post has the same net effect on DOF.

Funny how elegantly that works out.

 

[Robert S]

How many times has this horse been beat and it still lives...


DOF is perception. Or perhaps more accurately an attempt to measure perception. The only portion of an image that is actually in focus is that which lies exactly on the focal plane. Beyond that what is/isn't sharp lies purely in the eyes of the beholder. DOF calculators/calculations are a mathematically attempt to normalize/standardize "acceptable limits" of focus in front of and behind the focal plane. Which based on the amount of discussion that this topic always generates is a futile effort. Based on the mathematical description of DOF cropping does indeed alter it. It's not a topic of debate. It's mathematical fact. Based purely on subjective human perception it's been my experience that those who manage to fill the frame on full frame sensors believe strongly that cropping alters DOF. Those who shoot cropped sensors and or crop heavily swear that DOF is not affected. Go figure.

I rekon you have a good grasp of what is going on. Maybe if we consider a technical camera and consider how DoF is achieved with it, it may be useful. Lots articles on the internet about it. I no longer use my Sinar. Too complicated, bit like a cut throat razer, simple construction, very complicated functions.

 

[NorthernFocus]

I rekon you have a good grasp of what is going on. Maybe if we consider a technical camera and consider how DoF is achieved with it, it may be useful. Lots articles on the internet about it. I no longer use my Sinar. Too complicated, bit like a cut throat razer, simple construction, very complicated functions.

Unfortunately on this topic the technical explanations don't seem to carry much weight. If they did we wouldn't have all this discussion. And half or more of the online pundits would be out of work.

 

[Robert S]

I found a couple of Canon extension tubes [ second hand ]. They should be here next week. I will then be able to stack my Sigma 2x and 1.4x extenders on the Canon 100-400. Even then I will probably crop. Once I have some test shots I will post them here. I anticipate a min f stop of f16 and focal length of ff equivalent of 1792mm. Cropping will result in an even higher effective ff equivalent. Be interesting to see if the IQ is usable and if I can still hand hold. At these extreme focal lengths even at f16 the DoF will be only 5cm at 10m focus distance. [ Taken from Cambridge in Colour Depth of Field calculator. ] I will mostly be at less than 10m focus distance so bokeh should not be a problem. If I get a dark background it will not matter anyway. The loss of 3 f stops using the stacked extenders shouldn't be a problem. The first photo I posted above was R7 800mm f11 1/800 sec. ISO 400 hand held.
Anyway I can only wait and see what happens.

 

[nmerc_photos]

In that context you're spot on. A 1.4x TC or an equivalent 1.4x crop in post has the same net effect on DOF.

Funny how elegantly that works out.

I think with these two comments, I finally understand my confusion in all this.

Cropping also reduces depth of field.

When Bill said the above, I read it as "cropping also reduces DOF (in addition to all these other things cropping does)" but I think he meant "cropping also reduces DOF (in the same way using a TC does)".

Is that correct?

If so, it's all finally coming together for me and I appreciate everyone's patience with my denseness..

 

[fcotterill]

As with his explanations of Exposure, including debunking the Exposure Triangle myth, Cinematographer John Hess has the intuition and breadth & depth of understanding to explain the optical physics in a real world context using simple desktop experimental apparatus.
Note the key takeaways at ~7:00, ~11:00 and ~14:00

 

[Len Shepherd]

it's not an impact that is easy to point out. a person will never know based on DOF, whether an image is fullsize or cropped - unless compared to a fullsize or cropped image of itself - which never happens outside of testing.

You raise an interesting detail
With the D500 alongside the D810 DX, the D500 put significantly more MP on the subject than cropping the D810 - and the D500 AF points covered 50% more of the viewfinder area.
Back then I found it difficult to distinguish between the quality of my DX and FX images - probably part because the image content was for me much more relevant than the camera format.
If Nikon introduced an around 33MP professional grade DX body I would buy one.
Much of the need for this type of debate in my opinion would evaporate.

 

[EricKlees]

You raise an interesting detail
With the D500 alongside the D810 DX, the D500 put significantly more MP on the subject than cropping the D810 - and the D500 AF points covered 50% more of the viewfinder area.
Back then I found it difficult to distinguish between the quality of my DX and FX images - probably part because the image content was for me much more relevant than the camera format.
If Nikon introduced an around 33MP professional grade DX body I would buy one.
Much of the need for this type of debate in my opinion would evaporate.

The D500 at 20.9mp has a pixel density of just over a FF 48mp. The FF D850 is a 45mp. That and the fact that I'm camera DX for is a 19.2mp file.

So I'm not surprised you had a hard time telling the difference. I could see slight differences cropped heavy in Lightroom

 

[Robert S]

As with his explanations of Exposure, including debunking the Exposure Triangle myth, Cinematographer John Hess has the intuition and breadth & depth of understanding to explain the optical physics in a real world context using simple desktop experimental apparatus.
Note the key takeaways at ~7:00, ~11:00 and ~14:00

Thanks for the post. Worth watching. I'm 73 and my eyes are not as good as they were. I did film photography then moved to digital. I still confuse myself by thinking in film terms rather than digital.
My take on things is that once you have run out of chit chat the best thing to do is take photographs and see what you get. In this new world of digital and chit chat on the net the problems increase. What monitor is the viewer using etc etc.
I might have said this before but it makes sense to me. "If I bought a Stradivarius violin it would not make any difference to my ability to play the violin" <--- I can't play the violin.
"If I bought the best audio system in the world it wouldn't make much difference because my hearing is shot and I have tinnitus."

 

[Thern]

I didn’t read the whole topic, so it will prolly be said before, but nonetheless
There’s one real difference between using a TC or cropping.
A TC when used correctly, which means one does not attempt to use it at distances beyond the distance where the subject fills the frame less than half, will make no difference with cropping in camera (or in pp)
If you want to shoot beyond that distance you’re better of cropping.
The TC will start to show less or more astigmatism, while cropping uses the best part of the COC.
There’s also a penalty regarding lighting (noise if so) which is equivalent to cropping but with the need for a higher shutterspeed due to the increase in focal length which may be unwanted when shooting in low lighting conditions.
I used to shoot the 800 F/5.6 with dedicated converter and the 180-400 F/4 TC, but despite the fact their converters where perfectly dialed in with the lens I selden used them.
(FYI after retirement at 52 I used to be a Wildlife reserve manager and did a lot of registrational photography in dimlit conditions)
So the answer to your question is, it makes no difference but in the right conditions.

 

[arbitrage]

The bottom line is you need to decide for yourself. If you own a TC then get out and figure it out...do some controlled tests, do some real world shooting.
If you don't own a TC it is probably worth buying one used and do the testing and if you don't like it sell it for minimal loss.

When I've done controlled tests the results are usually a wash and I'm viewing at 300% in LR to try and nitpick the differences. But there are a lot of variables that go into it.
Are you shooting BIF? AF is never as good with TCs and IMO you are almost always better to just crop and use the greater FOV and better AF to have a higher success rate. Plus you can keep a 1 stop faster SS for a given f/stop and ISO.

For perched birds I think the TC can make sense sometimes. If you can lower SS and leave ISO the same then the TC can work in your favour. You don't need the better AF or wider FOV to track the bird like you benefit from with BIF.

I used to be a huge TC fan and at one point I had both EFIII TCs, all 3 Nikon F TCs and both Sony TCs in my bag...LOL
Over the past 3-5 years I've migrated away from TCs. I much prefer shooting my 600/4 and 400/2.8 bare lens and cropping as needed.
However, I've started to change my mind back to TC use with my new 300/2.8 GM....something with that lens just takes TCs so well that I'm finding AF is so good I can use it with TCs and I think I'm getting better results when 600 is needed and 300 is much too short.

I find it a confusing and conflicting topic for myself. I experiment and if I'm happy back at the computer then I continue to use one, if not, I stick to the bare lens and crop (often a lot).

 

[Thern]

Yup it’s a very personal experience and the faster (AF and aperture) the lens and the higher the resolving power of the bare lens the better the results will be when using a TC.
(Again depending on one’s typical shooting conditions)
I don’t shoot Nikon anymore so I’m not familiar with the quality of the current TC’s but I imagine they’re as good maybe even better than their Canon and Sony contenders back in the F-mount days.
Good recommendation Geoff

 

[Andy A.]

Yes! Z8 using the Z180-600mm lens

I would always opt for DX Crop Bob, for all the reasons mentioned. I use a Z9 and always think of DX crop mode as a "D500 on Steroids" function. Plus it sometimes helps subject detection find the eye in suboptimal light.

 

[bleirer]

I think with these two comments, I finally understand my confusion in all this.



When Bill said the above, I read it as "cropping also reduces DOF (in addition to all these other things cropping does)" but I think he meant "cropping also reduces DOF (in the same way using a TC does)".

Is that correct?

If so, it's all finally coming together for me and I appreciate everyone's patience with my denseness..

An argument was being made at the time that a good reason to crop instead of TC was that cropping doesn't affect DOF but the TC does, so the implication was that it was in the pro column for cropping. I just pointed out that it shouldn't be in the pro column for that reason. But there are other good reasons to crop and other good reasons to TC.

 

[bleirer]

As with his explanations of Exposure, including debunking the Exposure Triangle myth, Cinematographer John Hess has the intuition and breadth & depth of understanding to explain the optical physics in a real world context using simple desktop experimental apparatus.
Note the key takeaways at ~7:00, ~11:00 and ~14:00

I like the quote in big bold letters around 10:15. "All other factors equal - the smaller sensor will have the shallower depth of field."

Good video, worth watching from the beginning. He goes on to explain equivalency and crop factor and why once adjusted by physically moving farther away to fill the sensor with the same size subject the dof increases (because of being farther away). However we have been talking about staying in the same place and by cropping effectively reducing the size of the sensor. At least that's how I see it.