APS-C Digital SLRs, Are they worth it over point and shoot?

dngrov257 · Sep 7, 2009

All,

I have owned a Canon Rebel XTi with a 17-85MM lens for about 2 years. I also own a 50MM 1.8 lens. We also own a Canon SD400 5.0 MGP Digital Elph.

Frankly, I am frustrated with my experience with the Rebel, which is admittedly compounded by the fact that the 17-85MM lens ($500) is no longer autofocusing, and I must send it back to Canon after only 2 years of moderate use.

However, my broken lens is giving me a chance to reevaluate digital photography. Although certainly not a professional, I used manual focus Nikon SLR's for nearly 30 years before I bought the Rebel. I quite familiar with basic photographic techniques.

The main frustration with the Rebel is that the APS-C sensor in combination with the 17-85MM f4-5.6 lens does not permit one to blur backgrounds. I bought the 50MM 1.8 for use as portrait lens, and even at 1.8 the background is blurred some, but not obliterated as it would be if I used my Nikon FM2 with a 50MM 1.8 lens. I sometimes wonder if the trend in wedding photography to show the bride and groom with the church, outside site, etc. in full focus in the background is simply a response of professional photographers shooting with digital SLRs with APS-C sensors because they cannot afford digital SLRs with full-sized sensors. My photography instructor in the 1970's would have considered failure to blur the background in portraiture to be poor technique.

However, the most frustrating thing is that I do not believe my Rebel XTi (10.1 MP) takes better photographs, particularly landscapes, than our 5.0 MP Canon Digital Elph. The Rebel and the lens cost me about $1400, whereas the Digital Elph cost me $250. The essential question is this: if one cannot blur the background with a APS-C sensor digital slr with a lens that most people can afford, then why not buy a good point and shoot, such as the Canon G10, instead?

Any thoughts or comments that you may have would be most appreciated.

IgsEMT · Sep 7, 2009

RECAP of what you're saying:
You don't like Canon equipment b/c it gives you hell and needs repairs.
You like your Nikon camera.
You don't like seeing large DOF.
SLR vs P&S

My response would be it makes no difference whether you're using Canon or Nikon (though I like Nikon). DOF, in wedding photography, is a matter of preference of photographer and the client. If client likes what he/she sees, photographer will continue deliver it. My flavor of DOF in wedding photography is around f/5.6 as the rest though nice but is less natural. My clientèle, prefers the look to be natural during both candits and formal portraits. The times when I do shoot f/2.8 is of a ring, a flower, bouquet, etc
SLR vs P&S - g10 isn't cheap thus for the same price slr is affordable. One advantage of SLR over G10 of G11 is simply control. I owned G10 for about 20days and as great as the camera was, I hated the colors on it. After playing with WB, color profiles and finally looking at results in print I returned it - BUT THATs me and it isn't Canon issue b/c I work with Canons on weekly bases.

astrostu · Sep 7, 2009

I think you're finding one aspect that you think a crop sensor cannot perform to your satisfaction and then saying that because of that one thing, an entire class of cameras is effectively useless (if a P&S is as good as the DSLR, then the DSLR is useless).

I'm sure there's a formal logical fallacy I could pull out of that, but I think it should be suffice to say that for the general user, your point is not an issue. There are so many things that you can do with a DSLR that you cannot do with a P&S that faulting one apparent short-coming is really not of importance. However, if for YOU a very shallow depth of focus is necessary and you think that you cannot achieve that because of a cropped sensor, then by all means, don't use the camera.

That said, your premise is incorrect. You can get perfectly blurred backgrounds with a cropped sensor. The basic optical formula that defines depth of field is:

Depth of Field = (2 * N * b * f^2 * d) / (f^4 - N^2 * b^2 * d^2)

where N = f/number, b = acceptable blurring, f = focal length of lens and d = distance to object. To simplify it to important parameters that would be apropos for a test:

Depth of Field ~ (N * f^2) / (f^4 - N^2)

This is important because, though the f/number would be the same in any given test that you would hopefully do, the focal length of the lens does change on an APS-C sensor to 1.6x and so to get the same field of view you will have to decrease the focal length by 1.6x on an APS-C camera. So, in order to get the same field of view you may expect from a 50mm lens on a full-frame sensor or film, you would have to use a 31mm lens on a body with an APS-C sensor ... and this will significantly increase the depth of field. On a P&S, the difference would be even greater because the sensor size is smaller.

A fix is simply to get farther from your subject so you can use a similar true focal length (50mm lens, but would act as an 80mm lens so you'd need to get farther away from your subject to have the same field of view). However, then that d factor comes into play, where the farther away you get, the more the depth of field will be for that focal distance. So, it's not a simple function where you can just get a little farther away for the same effect. Rather, you would have to increase your distance more, increase your focal length more, and/or decrease your aperture.

So, optically speaking, the sensor size has nothing to do with the depth of field. It only has to do with the scene composition, which then has an effect on the depth of field due to focal length requirements.

But, when all is said and done, as I said before you can get nice, blurred backgrounds with a cropped body. These are just two examples that I happened to have uploaded, and both were at 200mm, f/4.5 when I could've shot at f/2.8 (with that lens):

KmH · Sep 7, 2009

"Any thoughts or comments that you may have would be most appreciated."

I second what Astrostu said, in that your premise is not valid.

Astrostu also pointed out that acheiving blurred backgrounds is even more difficult with the small sensor in a P&S.

You might want to play with some numbers at www.dofmaster.com .

As far as getting better landscape images with the P&S over the DSLR? Better in what way? Are you capturing image with the DSLR in the RAW data format? Or the JPEG image format?

Derrel · Sep 7, 2009

The original poster wrote, "I sometimes wonder if the trend in wedding photography to show the bride and groom with the church, outside site, etc. in full focus in the background is simply a response of professional photographers shooting with digital SLRs with APS-C sensors because they cannot afford digital SLRs with full-sized sensors. My photography instructor in the 1970's would have considered failure to blur the background in portraiture to be poor technique."

My answer to that is "Yes!". Until recently, full frame digital slr bodies were priced in the $7995 range. Prices slowly went down, with the EOS 5D priced around $3,200 at introduction,as I recall. The prices have slowly come down, with the last generation being priced at $2799 and $2995 (Canon and Nikon, and Sony at just under $3k). Note that astrostu's samples of the bird and squirrel cover a Field of View of apprx. 20 inches wide at perhaps 10 feet at 200mm at f/4.5, with a "relatively" distant background: that example is not representative of wedding photography or people photography. The examples show the very-strongest area of APS-C's shallow DOF potential, but only on very small areas, shot close,with a long lens. The bird and squirrel samples have very little to do with people photography; 20 inches of a person is a tight head and chest shot The samples shown do not apply to the OP's question about wedding photography, or event photography.

The capture format size of FF is 864 square millimeters, APS-C Nikon is 370 square millimeters, and APS-C Canon is 329 square millimeters. The Olympus 4/3 system is 17.3x 13mm or 225 square millimeters; the old Instamatic 110 format was 17 x 11 mm.

The proliferation and cost of APS-C d-slrs has meant that may wedding shooters, many of whom cannot or could not afford $7995 full frame cameras bought APS-C cameras back when those were $2400 or so, and continued buying them as the prices steadily went down. Many wedding shooters like the easy operation and the deep depth of field that small-format cameras bring. At typical flash and outdoor fill-flash apertures, which are limited by camera ISO and top flash synch speeds, APS-C cameras with 1/250 or 1/200 X-synch and 200 ISO minimums force photographers into DEEP depth of field exposures, like f/13 at 1/200 at ISO 200,and so the camera itself, is the driving force. Sort of "the cart pulling the horse".

Still, APS-C cameras offer more selective focusing options than do small-sensor digicams. It *is* possible to get shallow DOF and out of focus backdrops with APS-C, but really, this is most easily done with close subjects that are relatively small, as shown in the examples from astrostu, who understands the limitations/characteristics of APS-C better than many less technically-inclined shooters. The problems with APS-C and achieving shallow DOF results from the small sensor and the concomitant short focal length lenses, and the Field Of View crop factor that forces the photographer to stand FAR AWAY from larger subjects in order to be able to frame them with a 1.5 to 1.6x reduction in every lens's field of view. The small APS-C sensor means that at longer shooting distances, the lens will be sufficiently approaching,or close enough to its hyperfocal distance,so that that the resulting photograph will have *DEEP* depth of field with basically, all wide-angle focal lengths shot past about 10 feet,and even the medium-telephoto lenses of 85mm will be sufficiently close to their hyperfocal distance that the backgrounds of things 35 to 50 feet away will be in fairly decent focus. APS-C demands extremely wide apertures to get shallow DOF in medium-range shooting, often paired with rather long focal length lenses as well. But, it makes pulling focus on group shots easier-many wedding shooters like that!

Just last week, I had a disagreement with a member here about the difficulty of throwing the backdrop out of focus with APS-C and a kit lens. After that disagreement, I happened to be at the state fair horse arena, and wanted to frame the American flag with the background not competing for attention with the subject, the flag in the foreground. The flag was hanging 50 feet from me on a support beam,and the background was ugly, and about 200 feet distant in the huge arena. Using my 20D and 18-55 at 55mm, wide open at f/5.6, I could *NOT* throw the background out of focus sufficiently, to bring visual emphasis to the flag in the foreground. The sensor was too small, the lens too short, and the camera-to-subject distance was too far: the overall depth of field was simply *not shallow enough*,and the entire background was recognizable and distracting. A shallow depth of field photo was simply impossible with the gear I had from that shooting position. Similar issues crop up all the time when doing people photography using a small-capture format camera. This deep DOF and this-lens-doesn't-quite-allow-me-to-use-it-indoors is why so many serious shooters are very happy that FF bodies are now more numerous (Canon has two current models,Nikon has three now, Sony has two now!) and lower-cost than ever before. A 28-70 used to be a good event lens on FF: now it is nearly useless.

Keep in mind your 1970's photo instructor was probably used to medium format cameras, with their large capture sizes, longer lenses, and much shallower DOF characteristics. A 150mm lens on 6x6 has *shallow* DOF,and makes foreground/background separation very easy to accomplish; the same thing is very difficult to do on APS-C when inside a normal-sized building or room. FF d-slrs' bring utility back to one's 50mm,85, and 100mm lenses indoors, and also at outdoor events. On APS-C, 85mm is sooooo narrow in angle of view that is is simply impossible to use in many rooms, because an 85mm lens requires a 35 to 60 foot shooting distance on APS-C in order to frame two people, or a medium-sized group of people. Your photo instructor's idea of how pictures ought to look was based on his own tastes and prevailing equipment; ever seen 1910's-era portraiture shot on 5x7 view cameras? DOF sufficient to pull the nose and eyes into focus, back of the head often wayyyyy out of focus....now that was shallow DOF!

dngrov257 · Sep 7, 2009

Derrell,

Thank you. Although I do not understand the technical details as does Astrostu, I am an experienced amateur photographer who has come to understand, whatever the technical stuff, that a picture taken with my 135MM Nikkor at 5.6 will have more pleasing bokeh than my Canon 17-85MM at 85MM (equivalent to 135mm) at 5.6. I find this particularly frustrating, but I cannot afford to purchase a DSLR with a full frame sensor, so I will have to live with the limitations of an APS-C sensor. When I want a nice portrait, I will get out my Nikon FM2 with the 105MM 2.5 and buy some film.

dngrov257 · Sep 7, 2009

Astrostu,
Thanks for the reply and you posted some very nice pics to prove your point. However, my comments are based on my experience in shooting portraits of people on the long end of my 17-85MM (28MM-135MM in 35MM) f4-5.6, as opposed to a 200MM lens, which is 300MM in 35MM equivalent. Although the background is out of focus when shooting at 85MM, f 5.6, it is not sufficiently blurry for a good portrait as it would be with my Nikkor 135MM at 5.6. This is my frustration with my Canon XTi. I simply cannot afford to buy a faster lens with a longer zoom range. If my collection of manual focus Nikkor lenses were worth anything in today’s market, maybe I could, but they are not worth in the digital, autofocus world.

astrostu · Sep 7, 2009

dngrov257 said:
Astrostu,
Thanks for the reply and you posted some very nice pics to prove your point. However, my comments are based on my experience in shooting portraits of people on the long end of my 17-85MM (28MM-135MM in 35MM) f4-5.6, as opposed to a 200MM lens, which is 300MM in 35MM equivalent. Although the background is out of focus when shooting at 85MM, f 5.6, it is not sufficiently blurry for a good portrait as it would be with my Nikkor 135MM at 5.6. This is my frustration with my Canon XTi. I simply cannot afford to buy a faster lens with a longer zoom range. If my collection of manual focus Nikkor lenses were worth anything in todays market, maybe I could, but they are not worth in the digital, autofocus world.

I tried to make three points in my post, but two were in the second paragraph and I think became overshadowed by my lengthy third. My first point was that there is a lot you can do with a cropped sensor DSLR that you cannot do with a P&S. External flashes, for your application, come to mind. But my second point was this:

However, if for YOU a very shallow depth of focus is necessary and you think that you cannot achieve that because of a cropped sensor, then by all means, don't use the camera.

In other words, if wedding photography or studio photography are your main areas of importance, and you cannot achieve the style that you want due to the physical laws of optics on a cropped body, then by all means, don't use the camera. Go back to your film, as you said you would. I'll add that the way I state this may sound harsh, but I mean it in a very matter-of-fact tone as opposed to holier-than-thou or condescending.

NateWagner · Sep 7, 2009

Although I don't know if this is useful, as the points have already clearly been stated, but...

In my experience, knowing how DOF works and interacts with aperture, distance from subjects and distance to background, greatly affects the images that are produced with a APS-C camera. Clearly an APS-C sensor has limitations, but they are far less restricting than those of a P&S when it comes to DOF.

For example in weddings and the like, if you're taking a photo of the B&G in front of the church it is still relatively easy to knock out the background using a 50mm 1.8 or even a 18-50 2.8 as long as you have the B&G close to the camera. If you are willing to go with a head and shoulders shot for example, you can easily get the blurred background.

In many cases though the B&G pick the church based on how pretty it is, so to completely demolish it for bokeh is a little odd in many cases. Shallow DOF can be useful in many cases, but also I think that the trend has always been there for a fair amount of DOF in cases that you mentioned such as the B&G in front of a church.

Derrel · Sep 7, 2009

dngrov257,
Thank you for the note of thanks to both me and to astrostu. Astrostu is right--the APS-C sensor has much more shallow DOF flexibility than a P&S with a very tiny sensor and its ultra-short focal length lenses and commensurately short hyperfocal distances. Dngrov257, your real-world experience showing the difference between the pleasingly defocused nature of a 135mm lens shot at f/5.6 on a FF Nikon and the less-than-ideal degree of background blur when using a Canon and 17-85mm lens shot at 85mm and set at f/5.6 is pretty familiar to many people who own 18-55 and 18-70 or 17-85 kit zooms of various makes.

One answer is to order an inexpensive Nikon F mount to Canon EF lens mount adapter from an eBay vendor, and use the 135 Nikkor on your XTi. I have about a dozen eBay-purchased adapters that allow me to use my most-commonly used Nikkor prime lenses on my Canon bodies. I bought an EOS 5D body a few years agom back when Nikon had NO full-frame options, and the Nikkor lenses like 50,60,85,105,135,180,and 200mm work well on EOX 20D and 5D. Manual focusing, and semi-automatic light metering.

Pentax M42 lenses and Olympus OM lenses are excellent choices for adapting to a Canon body,and have the added benefit of an Auto-Manual diaphragm stop-down button or switch, which can be instantly depressed to bring the lens from wide-open, and down to the stopped-down or "taking" aperture with the press of a button. Older M42 thread mount Pentax lenses are available very cheaply. These simple adapters cost about $17 from eBay vendors such as the one located in League City,Texas.

I know it might not be the ideal solution, but the inexpensive eBay adapters DO WORK quite well,and bring 30+ million manual focus Nikons, as well as AF and AF-D Nikkors (something like 15 million of those), into focus on Canon d-slr bodies, with complete infinity focus without glass adapters. M42 thread mount lenses and Olympus OM-mount lenses have turned into basically dead-ends, so the prices on those are very low. Pawnshops and junk stores have a lot of M42 and OM stuff gathering dust since there are basically no new bodies that those lenses will directly mount to. It's a buyer's market on M42 and OM mount primes,and the quality of many of the older lenses is surprisingly high.